Chiral Surfactant-Type Catalyst: Enantioselective Reduction of Long-Chain Aliphatic Ketoesters in Water

Abstract

A series of amphiphilic ligands were designed and synthesized. The rhodium complexes with the ligands were applied to the asymmetric transfer hydrogenation of broad range of long-chained aliphatic ketoesters in neat water. Quantitative conversion and excellent enantioselectivity (up to 99% ee) was observed for α-, β-, γ-, δ- and ε-ketoesters as well as for α- and β-acyloxyketone using chiral surfactant-type catalyst 2. The CH/π interaction and the strong hydrophobic interaction of long aliphatic chains between the catalyst and the substrate in the metallomicelle core played a key role in the catalytic transition state. Synergistic effects between the metal-catalyzed site and the hydrophobic microenvironment of the core in the micelle contributed to high stereoselectivity.

2-Oxoesters: A Novel Class of Potent and Selective Inhibitors of Cytosolic Group IVA Phospholipase A2

“…Yield 73%; White solid; mp: 53–55 °C; 1 H NMR (200 MHz, CDCl 3 ): δ 3.85 (s, 3 H), 2.82 (t, J = 7.2 Hz, 2 H), 1.70–1.51 (m, 2 H), 1.37–1.16 (m, 22 H), 0.86 (t, J = 7.0 Hz, 3 H); 13 C NMR (50 MHz, CDCl 3 ): δ 194.3, 161.5, 52.8, 39.3, 31.9, 29.6, 29.5, 29.4, 29.3, 29.2, 28.9, 22.9, 22.6, 14.1; MS (m/z, ESI): [M + NH 4 ] + calcd. for C 17 H 32 O 3 302.3; found, 302.3 61 .…”

Cooperative effects of ruthenium micellar catalysts and added surfactants in transfer hydrogenation of ketones in water

“…[4][5][6][7][8][9] Although water is a cheap and environmentally benign solvent, water-insoluble (apolar) substrates are difficult targets for aqueous-phase reactions. [15][16][17][18][19][20][21][22][23][24][25][26] Generally, a surfactant is added to an aqueous solution of a catalyst for preparing the micellar system; more rarely surface-active catalysts are employed. [15][16][17][18][19][20][21][22][23][24][25][26] Generally, a surfactant is added to an aqueous solution of a catalyst for preparing the micellar system; more rarely surface-active catalysts are employed.…”

“…[15][16][17][18][19][20][21][22][23][24][25][26] Generally, a surfactant is added to an aqueous solution of a catalyst for preparing the micellar system; more rarely surface-active catalysts are employed. 18,22,27 At the same time the surface active catalysts can dramatically improve the reaction rate of TH, particularly of water-insoluble substrates, 19,[23][24][25] however the effect of the added surfactants have been never studied for them. For aqueous transfer hydrogenation of ketones catalyzed by non-micellar ruthenium/rhodium complexes, the added surfactants have been shown to have various effects depending on the type of surfactant used.…”

“…The micellar approach helps to overcome the phase-transfer limitations for water-organic catalytic systems and has been employed for many catalytic transformations [10][11][12][13][14] including (transfer) hydrogenation. [15][16][17][18][19][20][21][22][23][24][25][26] Generally, a surfactant is added to an aqueous solution of the catalyst to prepare a micellar system; more rarely, surface-active catalysts are employed. Despite the numerous papers on TH of carbonylic substrates that have been published, the effect of the added surfactant is scarcely investigated.…”

Vancomycin-Iridium (III) Interaction: An Unexplored Route for Enantioselective Imine Reduction

“…This reaction is a key tool to produce complex alkaloids and un-natural β-amino acids as well as important pharmaceutical intermediates [18,19,20,21]. In this regard, Asymmetric Transfer Hydrogenation (ATH) provides a valuable process and Ir(III) catalyzed ATH has been recently widely investigated due to the possibility to use environmentally friendly reaction conditions as the aqueous media for both the reduction of imines and ketones [22,23,24,25,26,27,28]. Generally, ruthenium and rhodium were used as co-factor for transfer hydrogenation reactions for involving ketones, even if in the last decades many researchers shed light on the potential use of iridium based catalysts, thus expanding the scope of reaction to imines.…”